An Organic Light-Emitting Diode (OLED) display is one of focuses in the research field of displays at present, and has low power consumption, a low production cost, self-light-emission, a wide angle of view, a high response speed, and other advantages as compared with a Liquid Crystal Display (LCD). At present, the OLED screen has come to take the place of the traditional LCD screen in the display fields of a mobile phone, a Personal Digital Assistant (PDA), a digital camera, etc., where the design of a pixel circuit is a core technology in the OLED display, and a research thereon is of great significance.
Unlike the LCD in which brightness is controlled using stable voltage, the OLED display, which is current-driven, needs to be controlled using stable current to emit light. There may be non-uniform threshold voltage Vth of driving transistors of pixel circuits due to a process factor, aging of elements, etc., so that current flowing through the different OLED pixels varies, and the pixels display at non-uniform brightness, thus degrading a display effect of the entire image. Although the threshold voltage of the driving transistor can be compensated for in the existing circuit scheme, some problem may remain, for example, a capacitance component and reference voltage is introduced to the light emission current so that it becomes more difficult to adjust gamma voltage in the pixel circuit, and there is a wider demand range of a data signal, thus discouraging power consumption from being lowered.
As illustrated in FIG. 1 which shows a schematic scheme diagram of a pixel circuit in the related art, for example, the circuit includes one driving transistor DT1, three switch transistors, and two capacitors, and threshold voltage of the driving transistor is compensated for in four stages including a node initialization stage, a threshold detection stage, a data writing stage, and a light emission stage. In one embodiment, as illustrated in FIG. 2 which shows a timing diagram corresponding to the pixel circuit illustrated in FIG. 1, in the node initialization stage, the first switch transistor T1 and the second switch transistor T2 are switched on, and the third switch transistor T3 is switched off, and at this time, voltage of the first node N1 is reference voltage Vref transmitted from a data signal terminal, and voltage of the second node N2 is a reset signal Vint transmitted from a reset signal terminal; in the threshold detection stage, the first switch transistor T1 and the third switch transistor T3 are switched on, and the second switch transistor T2 is switched off, and at this time, the voltage of the first node N1 is the reference voltage Vref transmitted from the data signal terminal, and the voltage of the second node N2 is Vref−Vth; in the data writing stage, the first switch transistor T1 and the driving transistor DT1 are switched on, and the second switch transistor T2 and the third switch transistor T3 are switched off, and at this time, the voltage of the first node N1 is a data signal Vdata transmitted from the data signal terminal, and the voltage of the second node N2 is VN2=Vref−Vth+C1/C1+C2+COLED(Vdata−Vref) due to the coupling of the capacitors; and in the light emission stage, the third switch transistor T3 and the driving transistor DT1 are switched on, and the first switch transistor T1 and the second switch transistor T2 are switched off, and at this time, driving current is I=K(C2+COLED)(Vdata−Vref)/(C1+C2+COLED), that is, the driving current is dependent upon the capacitors, the voltage of the data signal terminal, and the reference voltage, thus making it more difficult to adjust gamma voltage in the pixel circuit, and widening a voltage demand range of the data signal, which may discourage power consumption from being lowered.